Description

During Leg 72 in the western South Atlantic, Cretaceous sediments were recovered only at Hole 516F (Rio Grande Rise). Late Cretaceous planktonic foraminifers were found in Cores 516F-89 through 516F-122 (between 964 and 1235 m sub-bottom); they are assigned to the late Coniacian to the latest Maestrichtian. Frequency and preservation of planktonic foraminifers are moderate in the upper Maestrichtian and deteriorate from there to the base. Only the upper Maestrichtian Abathomphalus mayaroensis Zone can be clearly delimited according to the generally accepted planktonic foraminiferal zonation; moreover, some of the more important zonal and stage boundary markers were not found. The Cretaceous/Tertiary boundary is well documented without any major hiatus, and in spite of the poorly recognized zonal boundaries, the Upper Cretaceous sequence is apparently continuous. There are possible correlations between planktonic foraminiferal distribution in Hole 516F and those in Site 356 (Sao Paulo Plateau) and Sites 357 and 21 (Rio Grande Rise).